I'm not sure this isn't a product of how large and optically uncompromised the 4/3s zooms were. It's hard to correct a lens as fully when compactness and light weight are leading priorities.

Large? I don' think they were too large but I agree that maybe we as users did not appreciate fully how good those lenses were.

Compare the size of the Oly 4/3 7-14 to that of the Panasonic m43 7-14,

A lot of the size savings from the 7-14 seem to be due to the mirror box in this case creating the need for a more complex design... Also the Olympus seems to have little to no issues unlike the Panasonic lens which has had a number o fhtreads about purple flare?

The purple-flare issue is due to the fact that a) the antireflective coatings on at least some of the lens elements of the 7-14 do not fully remove reflections close to the border between ultraviolet and violet and b) the on-sensor UV-filter on most/all Oly bodies, unlike that in most/all Panasonic bodies, does not eliminate these wavelengths. It has nothing whatsoever to do with the issue discussed in this thread. See here for additional details:

Not a thorough review, but there is clearly a difference. As the 14-35 is a better performing lens then the 12-60 it simply is what it is.

There is no free lunch, software correction and slow apertures will make smaller lenses. These smaller lenses will not outperform larger lenses for IQ reasons, they will have different advantages (size portability, comfort in use, price etc.)

What evidence can you muster in support of your claim that the smaller lenses MFT lenses cannot outperform the larger FT lenses, everything else equal (including max aperture).

WHat does all else being equal mean? If I stop the 12-60 down to f5.6 and compare images to the kit zoom wide open i think the results will be obvious. My phrasing was slightly off as I was in a hurry, by larger my contention was that a faster lens such as the 12-60 vs the 12-50 (as brought up by steve) the 12-50 cannot keep up.

Now the 12-40 f2.8 may well be a sharper lens, and it is smaller than the 12-60, but it takes advantage of the mirrorless design, uses digital correction (which I dont hold anything against) and is 20mm shorter at the telephoto end.

So there are real differences beyond just it being a m43rds lens. Plus it is actually quite alot larger than the average m43rds zoom... My guess it to keep the quality higher.

Before going into detail, just a question to make sure we don't debate things we actually agree on: What is the general point you are trying to make? That the smaller MFT lenses are generally optically inferior to the larger FT lenses since the former, on account of being smaller, must by definition perform less well than latter when the two are compared at the same f-stop?

If not, please spell out as clearly as you can what your general point is.